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    <title>SNAP Data Processors - MERIS/(A)ATSR SMAC Atmospheric Correction </title>
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        <td class="header">&nbsp;
            MERIS/(A)ATSR SMAC Atmospheric Correction - Processor Description
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<h3>Processor Description</h3>

<h4>I/O Parameters Tab</h4>

<p align="center"><img src="images/IOParameters.png"></p>
<h5>Source Product Group</h5>

<p class="i1">
    <b>Name: </b>
    Used to select the spectral source product. The source product shall
    contain spectral bands providing a source spectrum at each pixel. Use the <b>...</b> button to
    open a data product currently not opened in the Sentinel Toolbox.
</p>

<h5>Target Product Group</h5>

<p class="i1">
    <b>Name:</b>
    Used to specify the name of the target product.
</p>

<p class="i1">
    <b>Save to:</b>
    Used to specify whether the target product should be saved to the file system. The
    combo box presents a list of file formats. If ENVISAT is selected the source product must be in ENVISAT format too.
</p>

<p class="i1">
    <b>Open in SNAP:</b>
    Used to specify whether the target product should be opened in the Sentinel Toolbox. When the
    target product is not saved, it is opened in the Sentinel Toolbox automatically.
</p>

<h4>Processing Parameters Tab</h4>

<p align="center"><img src="images/ProcessParameters.png">
</p>
<ol>
    <p class="i1">
        <b>Aerosol optical depth: </b><br>
        Select the aerosol optical depth by either typing in a value for the optical depth or for the
        horizontal visibility. Both values are updated simultaneously using the Koschmieder formula.
    </p>

    <p class="i1">
        <b>Relative humidity: </b><br>
        Select the water vapour content in <i>g/cm<sup>2</sup></i> to be used throughout the scene.
        Option is disabled when using the ECMWF data.
    </p>

    <p class="i1">
        <b>Ozone content: </b><br>
        Select the ozone content in <i>cm * atm</i> to be used throughout the scene. Option
        is disabled when using the ECMWF data.
    </p>

    <p class="i1">
        <b>Surface pressure: </b><br>
        Select the surface pressure in <i>hPa</i> to be used throughout the scene. Option
        is disabled when using the ECMWF data.
    </p>

    <p class="i1">
        <b>Use MERIS ECMWF data </b><br>
        Select whether to use the MERIS ECMWF data for surface air pressure, ozone
        content and relative humidity. This option is disabled when the input product type
        is not MERIS L1b. Additionally this turns the surface air pressure correction
        using the digital elevation model on or off.
    </p>

    <p class="i1">
        <b>Aerosol type: </b><br>
        Select an aerosol type. The type can be either <b>CONTINENTAL</b> or <b>DESERT</b>.
    </p>

    <p class="i1">
        <b>Default reflectance for invalid pixel: </b><br>
        Specifies the value to be written to the output when the
        processor detects an invalid condition (either by the pixel being masked out
        or by a processing failure e.g division by zero).
    </p>

    <p class="i1">
        <b>Mask expression for the whole view (MERIS) or the nadir view (AATSR): </b><br>
        Specifies a mask expression which will be checked during processing. You can either type the expression
        manually into the text field or use the expression editor by pressing the edit button to the right.
    </p>

    <p class="i1">
        <b>Mask expression for the forward view (AATSR only): </b><br>
        Specifies a mask expression which will be checked during processing. You can either type the expression
        manually into the text field or use the expression editor by pressing the edit button to the right.
    </p>


    <p class="i1">
        <b>Bands to process:</b> <br>Select
        one or many bands to be atmospherically corrected from the predefined list
        of bands. Press "Shift" when clicking in the list to select a range of bands.
        Press "Ctrl" when clicking in the list to add a single band to the selection
        (only available when an input product is already selected).
    </p>

</ol>

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